Help I Ran Into A Problem

i took in 6 graduation cakes friday. the 1st one is due wednesday. i'm doing two 12 by 18 side by side.now here comes the problem. i can't find a big enough box to fit them?any idea where i can order them from? i'm in new olreans if that will help!!

I work in a bakery and when we have specialty cakes that won't fit in a regular sized box, we put two full size sheet cake boxes together, just leave the ends of the two unlatched, and slide them into each other till they are the size that you need. Then, just tape them together. Do the same with the tops. HTH